<p>Set the <code>r</code> attribute of the subelement relatively to the circumscribed size (length of the diagonal of the bounding box) of the element referenced by the selector in the <code>ref</code> attribute. If the value is in the <code>[0, 1]</code> interval (or expressed in percentages, e.g. <code>'80%'</code>), the <code>r</code> of the subelement will be set as a percentage of the size of the referenced element. If the value is <code>&lt;0</code> or <code>&gt;1</code>, the size of the subelement will be smaller/bigger than the size of the referenced element by the amount specified. Note that this makes sense only for SVG elements that support <code>r</code> attribute, such as <code>&lt;circle&gt;</code>.
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